The utility of CVD Al.sub.2 O.sub.3 as a reactive ion etch (RIE) stop layer (during tungsten contact stud patterning) has been clearly demonstrated. For this application, a dense aluminum oxide film is defined as having the following characteristics:
Index of refraction: 1.59-1.62, at 632.8 wavelength PA0 Etch rate (3.6% phosphoric acid at 75.degree. C.): &lt;25 nm/min PA0 Hydroxyl content (OH, by infrared (IR) spectroscopy, absorbance per micron of film thickness at 3500 cm.sup.-1): &lt;0.005 PA0 Shrinkage of film thickness upon annealing (30 min. at 500.degree. C.): &lt;1.5%
The literature indicates that aluminum tri-isopropoxide (Al(OC.sub.3 H.sub.7)), known in the art as ATI, is a viable sub-500.degree. C. Al.sub.2 O.sub.3 precursor. See, for example, J. A. Aboaf, J. Electrochem. Soc., 114, 948 (1967), J. Fournier et al., Mat. Res. Bull., 23, 31 (1988), J. Kwon, J. Saraie and Y. Yodogawa, J. Electrochem Soc., 132, 890 (1985), H. Mutoh et al., J. Electrochem. Soc., 122,987 (1975), and R. W. J. Morssinkhof et al., "Mechanistic Aspects of the Deposition of Thin Alumina Films Deposited by MOCVD", paper presented at Spring Meeting of the Materials Research Society, San Francisco, Calif. (1990). In these references, ATI is utilized under conditions in which 1) only bubbling is used to deliver ATI to the reactor, 2) a variety of ATI operating temperatures (78.degree.-170.degree. C.) is practiced, 3) deposition repeatability is not demonstrated, and 4) only a single substrate requires coating. However, while the literature describes the use of ATI for Al.sub.2 O.sub.3 deposition, the literature describes bubbling techniques for delivery of ATI but fails to present a workable manufacturing process. In fact, the bubbling technique described in the literature will not work in a manufacturing environment for the reasons discussed in more detail below.